1. Field
Embodiments of the present invention relate in general to orthodontics. More particularly, embodiments of the present invention relate generally to active attachment devices that interact with a polymeric shell dental appliance to provide additional forces on a patient's dentition.
2. Related Art
Orthodontic treatments involve repositioning misaligned teeth and improving bite configurations for improved cosmetic appearance and dental function. Repositioning is typically accomplished by applying gentle controlled forces to a patient's teeth over an extended period of time. Due to the limited space within the oral cavity and extensive movements that some teeth must undergo, the teeth will often be moved throughout a series of intermediate patterns to properly arrange the teeth. For example, molars may be temporarily moved backwards (distalized) to create adequate space for movement of the incisors. Thus, a single patient treated with plastic aligners may experience an average of 25-30 aligner stages before achieving the final desired teeth arrangement.
Conventionally, repositioning of teeth has been accomplished by what are commonly referred to as “braces.” Braces comprise a variety of appliances such as brackets, bands, archwires, ligatures, and O-rings. After they are bonded to the teeth, periodic meetings with the treating dentist are required to adjust the braces. This involves installing different archwires having different force-inducing properties, and/or replacing or tightening existing ligatures. Between the periodic meetings with the doctor, the patient may be required to wear supplementary appliances, such as elastic bands or headgear, to supply additional or extraoral forces. Although conventional braces are effective, their use is often a tedious and time consuming process and requires many visits to the doctor's office. Moreover, from the patient's perspective, the use of braces is unsightly, uncomfortable, presents a risk of plaque retention, and makes brushing, flossing, and other dental hygiene procedures difficult. Additionally, as conventional braces are fixedly bonded to the patient's teeth, the braces cannot be removed when the patient is eating.
An alternative to braces includes the use of elastic positioning appliances for realigning teeth. Such an appliance may be comprised of a thin shell of elastic material that generally conforms to a patient's teeth but each appliance is slightly out of alignment with the initial tooth configuration. Placement of the elastic positioning appliances over the teeth applies controlled forces in specific locations to gradually move the teeth into a new configuration. Repetition of this process with successive appliances comprising new configurations eventually moves the teeth through a series of intermediate arrangements to a final desired arrangement.
With traditional wire and bracket technology, the wire is tied to the bracket, such that the energy stored in the wire during the process of engaging the wire to the bracket gets released and converted into orthodontic tooth movement as the wire conforms back to this original undistorted shape. Shape memory alloys, for example, enable distortions that are stored in the wire to be gradually released over long periods of time.
Treatment using removable elastic positioning appliances occurs over increments of time. This occurs since the plasticity of the elastic positioning appliance is typically limited to a period of less than one week. That is, the elasticity of the elastic positioning device deteriorates quickly over a short period of time. As such, forces stored within the elastic positioning appliance typically can only be effectively applied over a period of approximately two weeks. As a result, a significant number of elastic positioning devices worn in stages are used over a long period of time to effectively provide orthodontic tooth movement.
Additionally, in some cases, orthodontic treatment may involve complex tooth movements or treatment plans requiring additional devices or accessories. That is, the forces applied by the removable elastic positioning appliances may not alone be sufficient to achieve these complex tooth movements or treatment plans. For example, the elastic positioning appliance alone may not be able to apply forces to surfaces of the teeth due to the location or characteristics of the surface itself of the tooth or of the surrounding teeth.